Theta synchronization coordinates ventral temporal and medial temporal coding of human face familiarity

Abstract

Summary Recognizing familiar faces is a fundamental social function that depends on interactions between perceptual and memory systems, yet the underlying neural mechanisms remain poorly understood. Here, we combine single-neuron recordings, intracranial electroencephalography (iEEG), and multi-scale connectivity analyses in the human ventral temporal cortex (VTC) and medial temporal lobe (MTL) to investigate the neural dynamics underlying face familiarity. Theta-frequency phase locking of MTL neurons is associated with face familiarity and familiarization, complementing firing-rate signals. The VTC represents visual features through an axis-based code that disproportionately contributes to familiarity representations. Familiarity is further associated with enhanced theta synchronization between the VTC and MTL, particularly between VTC visual-feature-coding and MTL familiarity-coding channels. Enhanced theta-frequency spike-iEEG coherence for familiar faces suggests that MTL phase locking is coordinated with large-scale VTC activity. Together, these findings identify theta synchronization as a key mechanism coordinating the neural dynamics underlying face familiarity processing in humans.